Complex interactions between the gut microbiota, pesticide contamination and physiological traits in grey partridges.

The intensification of agriculture in recent years, particularly through the massive use of pesticides and fertilizers, has caused a decline in biodiversity, specifically among farmland birds. Emerging research highlights the adverse effects of chronic and low-dose pesticide exposure, particularly on the gut microbiota, which is essential for host metabolism and immune health. Understanding how pesticides disrupt microbial diversity and physiological traits is therefore critical to inform management and conservation strategies. This study examines the impact of pesticide contamination on the gut microbiota composition and physiological responses of captive-bred male grey partridges, a threatened species frequently exposed to pesticide cocktail residues through their habitat and diet. We detected residues of 27 pesticides in the birds' blood, including fungicides, herbicides, and insecticides. Among the different microbial diversity metrics analysed, only MOTU richness was significantly affected by the interaction between pesticide load and body condition, with contrasting effects observed across different body condition groups. Furthermore, higher microbial diversity was positively associated with hematocrit levels, suggesting that microbial diversity may be related to the physiological health of birds. These findings highlight the complex relationship between pesticide exposure, gut microbiota, and host physiology, emphasizing the need for further research to understand these interactions in wildlife health.